Spin Resonance Studies on free Electrons and Defects in Microcrystalline Silicon

1994 ◽  
Vol 358 ◽  
Author(s):  
C. Malten ◽  
F. Finger ◽  
P. Hapke ◽  
T. Kulessa ◽  
C. Walker ◽  
...  
Keyword(s):  
Electron Spin Resonance ◽  
Grain Boundaries ◽  
Amorphous Phase ◽  
Electron Spin ◽  
Degree Of Crystallinity ◽  
Microcrystalline Silicon ◽  
Free Electrons ◽  
Conduction Band Offset ◽  
Spin Resonance ◽  
Material Points

ABSTRACTThe effect of micro-doping, defect creation, and non-steady state occupation through optical transitions on the electron spin resonance signals found in undoped and weakly doped microcrystalline silicon with a high degree of crystallinity is investigated. The experimental results are in agreement with the assignment of the resonance at g=1.9983 to conduction electrons in the crystalline grains and the resonanccs around g=2.0052 to dangling bonds in the remaining amorphous phase and at the grain boundaries. The simultaneous presence of both resonances can result from a large conduction band offset between crystalline grains and grain boundaries or the amorphous phase. The presence of conduction electron spin resonance in compensated and even p-type material points also to potential fluctuations. Free electrons in interconnected crystalline grains are in agreement with the weakly activated transport found in µc-Si:H at low temperatures.

Free electrons and defects in microcrystalline silicon studied by electron spin resonance

1994 ◽  
Vol 70 (4) ◽  
pp. 247-254 ◽  
Author(s):  
F. Finger ◽  
C. Malten ◽  
P. Hapke ◽  
R. Carius ◽  
R. Flückiger ◽  
...  
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Microcrystalline Silicon ◽  
Free Electrons ◽  
Spin Resonance

Defect and Tail States in Microcrystalline Silicon investigated by pulsed ESR

2000 ◽  
Vol 609 ◽  
Author(s):  
P. Kanschat ◽  
H. Mell ◽  
K. Lips ◽  
W. Fuhs
Keyword(s):  
Electron Spin Resonance ◽  
Detailed Analysis ◽  
Electron Spin ◽  
Qualitative Model ◽  
Dangling Bond ◽  
Microcrystalline Silicon ◽  
Band Tail ◽  
Spin Resonance ◽  
Donor States ◽  
Broad Structure

ABSTRACTWe report on a detailed analysis of paramagnetic states in a doping series of microcrystalline silicon, μc-Si:H, by pulsed electron spin resonance. We identify two dangling bond like structures at g = 2.0052 (db1) and g = 2.0043 (db2). Whereas db1 is evenly distributed in the gap, the db2 state is found to be localized in the lower part of the gap. The CE resonance at g ≈ 1.998 is assigned to electrons in conduction band tail states. In p-doped samples, we observe a broad structure CH at g ≈ 2.08 which we identify with holes trapped in valence band tail states. It is shown that the CH state behaves very similar on illumination as the CE resonance. In n-type samples a pair of hyperfine split lines (A ≈ 11 mT) is found which apparently does not originate from 31P-donor states. On the basis of our results we propose a qualitative model for paramagnetic states in μc-Si:H.

Photocarrier Recombination in Microcrystalline Silicon Studied by Light Induced Electron Spin Resonance Transients

1996 ◽  
Vol 452 ◽  
Author(s):  
J. Müller ◽  
F. Finger ◽  
C. Malten ◽  
H. Wagner
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Doping Level ◽  
Infrared Light ◽  
Microcrystalline Silicon ◽  
Excitation Energies ◽  
Time Resolved ◽  
Dark Light ◽  
Spin Resonance ◽  
Initial Excitation

AbstractTo get information on the density of states distribution and the photocarrier recombination in microcrystalline silicon (μc-Si:H), samples with various amounts of n- and p-type doping are studied with electron spin resonance (ESR) and stationary and time-resolved light induced ESR. The intensity of the dark ESR signals from dangling bonds (DB) and conduction electrons (CESR) is investigated as a function of the doping level. The DB signal has a flat distribution over a wide doping range while the CESR signal strongly increases with n-type doping. Upon illumination with white or infrared light both resonances are enhanced with an intensity that depends on the doping level. The decay of the light induced signal and the dependence in time and intensity of the residual signal on different initial excitation energies and dark/light -sequences is studied. The results are discussed with a schematic band diagram for μc-Si:H. The existence of a potential barrier is proposed which spatially separates photogenerated carriers. A large band-offset between crystalline and disordered regions is further suggested.

Infrared Absorption and Electron Spin Resonance Studies of Nanocrystalline Cubic Boron Nitride/Amorphous Hydrogenated Boron Nitride Mixed Phase Thin Films

1995 ◽  
Vol 395 ◽  
Author(s):  
Shu-han Lin ◽  
Ian M. Brown ◽  
Bernard J. Feldman
Keyword(s):  
Thin Films ◽  
Electron Spin Resonance ◽  
Boron Nitride ◽  
Hyperfine Structure ◽  
Amorphous Phase ◽  
Electron Spin ◽  
Infrared Absorption ◽  
Cubic Boron Nitride ◽  
Nanocrystalline Phase ◽  
Spin Resonance

ABSTRACTBoth infrared absorption (IR) and electron spin resonance (ESR) spectroscopies have been used to investigate the complicated structure of nanocrystalline cubic boron nitride/amorphous hydro-genated boron nitride thin films. The ESR spectra from this material consist of a component with a four-line hyperfine structure and/or a component with a ten-line hyperfine structure superimposed upon a broad central line. The hyperfine structures are associated with defect centers located in the nanocrystalline phase, whereas the broad line is attributed to dangling bonds in the amorphous phase. The IR spectra consist of three lines around 1400 cm−1: the lines at 1263 and 1505 cm−1 originate in a boron-poor amorphous hydrogenated boron nitride region; the line at 1371 cm−1, in a boron-rich amorphous hydrogenated boron nitride region. These results, together with previously reported electron diffraction spectra, suggest the following picture: small (2.5 nm) nanocrys-tallites of cubic boron nitride (about 5% of the material) are imbedded in a mixed amorphous phase. The amorphous region can be approximated by a mixture of boron-rich and boron-poor amorphous hydrogenated boron nitride.

Atmospheric aging and light-induced degradation of amorphous and nanostructured silicon using photoconductivity and electron spin resonance

2014 ◽  
Vol 92 (7/8) ◽  
pp. 713-717 ◽  
Author(s):  
Z.M. Saleh ◽  
G. Nogay ◽  
E. Ozkol ◽  
G. Yilmaz ◽  
M. Sagban ◽  
...  
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Light Exposure ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Pure Oxygen ◽  
Microcrystalline Silicon ◽  
Nanostructured Silicon ◽  
Dual Beam ◽  
Spin Resonance

Previous studies indicate that the dark conductivity in amorphous and microcrystalline silicon may increase or decrease with exposure to deionized water (DIW) or pure oxygen at 80 °C but always decreases with light exposure. While the light-induced effect is linked to paramagnetic dangling bonds (Do), the origin of metastability in microcrystalline silicon remains unclear. In this study, we use steady-state photoconductivity (SSPC), dual-beam photoconductivity (DBP), and electron spin resonance (ESR), to study the behaviors under soaking in DIW and (or) pure oxygen at 80 °C and light-exposure of amorphous (a-Si:H) and nanostructured (nc-Si:H) silicon samples deposited in a capacitively coupled plasma-enhanced chemical vapor deposition system. Powders from thick samples of low and high crystallinity (Xc) peeling off large substrates were collected in quartz tubes for ESR measurements. Dark conductivity decreases upon exposure to pure oxygen at 80 °C for nc-Si:H but remains unchanged for a-Si:H. The ESR signal attributed to Do decreases with soaking in DIW for high and low crystallinity nc-Si:H but the effect is more significant for higher Xc. Changes in SSPC, DBP, and ESR are used to compare the degradation mechanisms because of O2 exposure and light for amorphous and nanostructured silicon.

Adsorption and Oxidation Effects in Microcrystalline Silicon

2003 ◽  
Vol 762 ◽  
Author(s):  
T. Dylla ◽  
F. Finger ◽  
R. Carius
Keyword(s):  
Electron Spin Resonance ◽  
Surface Area ◽  
Electron Spin ◽  
Active Surface ◽  
Mixed Phase ◽  
Active Surface Area ◽  
Conductivity Measurements ◽  
Microcrystalline Silicon ◽  
Spin Resonance ◽  
Irreversible Effects

AbstractElectron spin resonance and conductivity measurements were used to study adsorption and oxidation effects on microcrystalline silicon with different structure compositions ranging from porous, highly crystalline to compact, mixed phase amorphous/crystalline. We found a correlation between active surface area and the magnitude of observed meta-stable and irreversible effects.

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